The "stars" rating system is not an objective way to measure the quality of the story, or product, it is a marketing tool to manipulate the consumers into buying by implying the expensive products are worth the extra cost because of supposed quality. It is never objective, it always leads to manipulations, and should be either ignored or completely abandoned.
While 2.5 star out of 5, or 5/10 (same thing, 10 point scale) is average from the purely mathematical standpoint, it's a middle value, it is already total failure from the marketing perspective it is used for.
In some cases, you have a complex algorithm that actively pushed down and hides the story under the certain threshold, like the Royal Road, where anything under the 4.5 star is on the way out, and anything below 4 is total failure. System is simply set up this way to sell the certain story, certain products in case of their Amazon's sugar daddy, and it doesn't care for the logical / mathematical standpoint. 3 stars on the 0.5 to 5 scale is actually above average already, but the system doesn't see it this way, even 4 is not enough.
In other cases, you have simply average the Scribble Hub uses; it isn't as unfair considering there doesn't seem a additional mechanism for hiding the stories the Amazon's Royal Road has, but damage was already done. Effect is psychological and many readers would unconsciously not read the story under the 4.5 threshold simply believing they are bad regardless of the objective quality, entirely forgetting that with one rating of 0.5 and one rating of 5, the average is 2.75 because they are not the mood or math and fixate on what the people designing this wanted. Highest values only, usually above 4.5.
Not to mention this system absolutely ruins the community, since not only people are naturally drawn to higher numbers which do not correspond to higher quality, all of them would try to game the system.
No one rates the stories on the objective scale of 1 to 5, or 1 to 10, they rate it on relative scale i.e. how much damage they want to do the story so the final value fits their worldview.
If you have a story that one person liked, and have only one rating, the second user who thinks your story is kinda average will not rate it 3 (or whatever the average value is), he will rate it lowest possible to inflict highest damage to balance the final score, and in the process, destroy the chance that the final rating would be objective, all because of human psychology.
